


Opposites Attract

by LittleLex



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), F/M, Fluff, Friends to Lovers, Kinda?, Kissing, M/M, Naga Sans, Other, Possessive Sans, Protective Sans, Reader and Sans both tease each other, Reader isn't having it, Reader lives alone and in the woods, Reader's gender not specified, They have a cute relationship, Tooth-Rotting Fluff, lazy sans
Language: English
Status: Completed
Published: 2021-01-23
Updated: 2021-01-23
Packaged: 2021-03-15 19:34:11
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,124
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28943769
Author URL: https://archiveofourown.org/users/LittleLex/pseuds/LittleLex
Summary: Somehow, you befriended a naga. He even lives at your house as well. On one particular day, Sans accompanies you as you do your usual schedule. However, he avoids a near disaster and that leads to something else.
Relationships: Sans (Underfell)/Reader, Sans (Undertale)/Reader
Comments: 6
Kudos: 81





	Opposites Attract

Somehow, you befriended a naga. A terrifying snake creature.

You lived alone in the forest and there were always rumors from your hometown that there lived a dangerous naga in there, but you never believed it. Until you were face-to-face with one.

His tail was long and a glimmering red with black stripes. His upper body was in the form of a skeleton, he didn’t look like a human skeleton. His bones were large and thick, almost fused. He had eye-sockets with one singular, piercing red eye-light inside of one. His tongue would occasionally slip out of his teeth, sniffing his surroundings. 

You found him injured one evening and ever since that day, he never stopped to visit you. You had to admit, you did enjoy his company. He flirted nonstop and he’d crack a joke every minute of every day. Although he was known to be a dangerous beast, you found him comforting. 

* * *

You hummed quietly to yourself as you finished loading the dishwasher. It wasn't a fun task, but it was necessary. Sans slithered behind you, waiting for you to be done to pounce on you, wrapping himself around you with his coils.

He tended to approach you like this. 

You made a noise of protest as he dragged you to the living room in front of the fireplace. He practically moved in with you, at first it was a few visits, but then he asserted himself into your home. You didn’t mind too much, it was nice to have company. However, when he demanded to have attention, he’d throw out anything you were doing to hang out with him. Those were the few downsides of the relationship. 

It was really your own fault he moved in. You treated him with kindness and love, nothing he’s ever seen before. It would only make sense he’d grow attached to you. He was cautious of you at the beginning, he even attempted to attack you when he woke up in your house until he realized you were the one who helped him. 

It took some time for him to come around, he’d watch you whenever you left the house to walk around the forest or pick berries from the bushes. Once he realized you weren’t a threat, (quite the opposite) he began to visit you. 

You sighed as Sans nuzzled your neck, snuggling you into the blankets of nests he created on the floor. It was one of his instincts as a snake, so it was only natural. You had enough blankets as it is, anyway. He purred loudly, feeling his ribs rumble with content.

“Sans…” You let out another sigh. He hummed innocently in response.

“You can’t just steal me whenever you want to, we talked about this.” You huffed. 

_ He had to protect you, to keep you safe. Although you weren’t aware, you were his mate, so it only made sense he had to be around to make sure.  _

“Mm…” He answered flatly. 

“Sans.” You stated more directly, hoping you got your point across.

“Yeah, baby?” 

You groaned. You didn’t really need to do anything else, you finished up your tasks. But, you had to make it clear to the naga of your concerns. 

“If you continue to ignore me, you won’t be allowed to stay here anymore.” You threatened. He immediately froze, drawing back from you just a bit. You almost snorted from his reaction. He looked like a boy who had just gotten caught staying past his bedtime. 

“Sans, you’re not really in trouble,” you started, “all I ask is you stop chasing me around to steal me, okay? You know I’m more than happy to give you affection, but there need to be boundaries for this to work.” 

He nodded slowly, albeit reluctantly. 

“Understand now?” He nodded again. You smiled, cupping his jawbone before nuzzling his nasal bridge. Dust of bright red covered over his cheekbones, your smile only widened. 

You conked out for the rest of the night without even realizing it. His warm body and the comfort of the blankets lulled you to sleep. You woke up, rubbing your eyes. You could barely move, as Sans’s tail kept you still. He clung to you like a baby monkey with his iron grip. 

You noticed the fireplace had been turned off, thankfully. You glanced over at the window, witnessing the silver moon brightest in the dark, starry sky. You considered just falling back asleep with Sans but decided sleeping in your bed would be a better option. 

It would be difficult slipping away from Sans, however.

Somehow, you managed to complete the task, successfully leaving him with a pillow to act as a piece of comfort for him. You tiptoed your way to your bedroom upstairs, shutting the door quietly, changing out of your clothes. 

* * *

Your eyes fluttered open, your brain fuzzy. You felt a warmth surround you and it wasn’t your blanket. Confused, your eyes darted downwards, realizing Sans had snuck into your room to fall asleep. 

This wasn’t anything new, he’d do this frequently. 

It was getting extremely hot under his body, especially with his coils pretzeled around you. You huffed, beginning to slip away from him, until you watched as he woke up, blinking slowly at you. 

“Wha…?” He mumbled. 

“Rise and shine, baby.” You teased. He whined as you left him, he had the extreme urge to pull you back, but he remembered your words from yesterday.

“Why don’t you get up with me for once, instead of sleeping in. Lazing the day away isn’t very productive.” You chastised. 

“I go out and hunt, ‘m plenty productive.” He retorted, you shivered.

His hunting was pretty grody, he’d kill any forest animals, like deer or bears, and eat them far away from you. He once tried to give you a dead, small animal as a ‘gift’, you flipped out. Ever since that day, he now eats outside, somewhere hidden in the forest. 

“Would you like to help me today?” You offered. It wouldn’t hurt if he accompanied you, maybe it would be beneficial for him. You didn’t appreciate how he just lounged about the house or outside, snoring the day away. Maybe he’d have a routine with you, maybe it would become a normal thing.

He sprung from his seat and slid behind you. Any hint of sleepiness was gone from his face. He seemed to like the idea, thankfully. You couldn’t help but smile at his antics.

“What’re we starting with first?” He inquired.

“Well, I have to change and use the bathroom, so you can’t be there for that.” You replied. He pouted at you, you rolled your eyes. 

“So… You can… Uh...” Your voice trailed on.

“I’m that useless, huh? If that’s the case I’ll go back to bed-” You grabbed him by his shoulder to prevent him from moving.

“Nope! You agreed, so you’re gonna help!” 

“Just wait for me downstairs.” You gestured with your hand before venturing off to the bathroom.

* * *

You caught the eye of Sans, who was taking a small nap on his nest. You sighed and as you were about to wake him up, his sockets opened, a toothy grin on his teeth.

“I can’t believe you fell asleep so quickly…” You muttered. He shrugged in response.

“Time flies while I’m waiting for you~” He winked suggestively. You _ tsked _ at him before heading off to the kitchen with him trailing behind you.

You didn’t feel up to making a full course meal, so toast would have to do. 

You popped the two slices of bread into the toaster, waiting for it to cook. “Not havin’ a five-star dish today, hm?” Sans whispered in your ear. You shook your head in response, leaving him to hum.

Your toast came out and you buttered it, eating the dry piece of bread. Sans waited patiently for you to actually begin his ‘work’. 

“I need to put all the stuff from the dishwasher away and I doubt you know where the stuff is, so I’ll do it quickly, then we can move on.” You explained as you opened the dishwasher, beginning to take the plates into the cabinets. You were shocked once Sans began to join you, shoving the utensils in the correct drawer. 

He laughed at your surprised reaction. “I watch ya all the time, I think I know where yer stuff is by heart, sweetie.” He snickered. Blush grew on your cheeks, you quickly shook your head before finishing taking everything out of the dishwasher.

The rest of the day went by smoothly, he successfully helped you with your tasks, adding in a few jokes here and there, some a bit dirtier than others. 

And now, you were out in the forest, picking berries that weren’t poisonous to you. Sans ate a few of them, even the ones that are dangerous to humans, which you yelped to him about. Sometimes you forgot he was a naga due to the fact of how comfortable you’ve gotten with him. 

You picked one of the berries and as you were about to drop it into your basket, a hand attached itself onto your wrist. You looked over as Sans snatched the berry away from your hand, munching on it greedily. You stomped your foot on the ground angrily.

“Sans! Stop eating so many berries, you’ll get sick!” You complained. 

He patted your head like a child. “You worry too much, I’m a big and strong serpent, I’ll be a-okay.” He assured you.

You scoffed in response, continuing to grab more berries. As you were about to leave the bush, a small patch of green caught your eye that was behind the bush you were currently picking. You shuffled closer to it and as you leaned closer to inspect it, your foot got caught on a root.

You yelped, preparing yourself to fall hard on the uneven, rocky ground, but the surface never hit you. Suddenly, Sans surrounded you, pulling you to safety in his arms. You were tucked to his chest, your basket dropped on the ground from your close fall. 

“Fuck, you okay, sweetheart?” He asked above you, concern dripping in his gruff tone. You merely nodded. 

He released you, picking up your basket before handing it over to you. There was a significantly less amount of berries in it. Oh well, you could always get more another day. He brushed a few strands of hair away from your face, tucking it under your ear.

“L-let's go back!” You shrieked, turning on your heel in embarrassment. 

* * *

The day had shifted into the darkness of the night. You were sprawled out on your bed, with Sans curled around you, not that you minded. You absentmindedly scratched his skull, hearing him purr contently in response. His tongue stuck out now and again, shifting up and down.

“Sans… Thank you for saving me earlier. I really appreciate it.” You softly spoke into the silence of the room. 

“Heh, who else would let a naga stay over at their place?” He shrugged it off, you didn’t miss how his cheeks dusted with red.

Your head shifted closer towards his skull, only a few inches apart. “No Sans, I really mean it. Even though you're kind of a slob, I enjoy your company here.” You pressed on. That only increased Sans’s blush. He spluttered, chuckling nervously. 

You knew you had feelings for the naga, there was no denying it. You were grateful you found him, he added more happiness to your life. You weren’t lonely anymore in your house. Yeah, you had friends, but you were deserted all by yourself, surrounded by greenery. Not to say you didn’t like it, but Sans gave you something more to your life. 

He gave you love.

You closed the gap between you two, passionately kissing his teeth. Although he lacked lips, the connection sent a pleasant spark within you, it was vibrant, strong, and powerful. Sans gave into the smooch, kissing you back needily, it was like he was waiting for this moment forever. 

He cupped your jaw, rubbing his phalange against your skin. You broke away from him, catching your breath. He started at you lovingly, his eye-light was in the form of a heart, nothing like you’ve ever seen before. 

“Sans, your eye… it’s a heart!” You excitedly pointed out. He blinked slowly, processing your words.

“Didn’t think I could do that…” He replied more to himself. A few giggles erupted from your lips. With another blink, the heart disappeared. You were a bit disappointed. You climbed onto him, sitting comfortably on the top of his tail. 

You pecked another kiss to his teeth. He kissed you back with power. 

It seems like your love was received. 

**Author's Note:**

> I love naga au!! I also love UF Sans, obviously. Why not combine two and two together?? I hope you all liked it! As always, stay safe and wear a mask. Don't forget to check me out on my Tumblr; little-lex.


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